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Condensation and Black Mould

Why is there black mould in my house? 

Black mould, also known by its other name Aspergilus Niger, is commonly associated with condensation which, in the UK, tends to be worse in the colder months when internal surface temperatures are cooler. 

Black mould is also associated with health problems relating to breathing such as Asthma and also skin irritation. Certain categories are more at risk such as the elderly, very young and those who are ill and immuno-depressed, being unable to fight off infection. 

The air conditions in internal living spaces in Winter are different than Summer. In Winter we tend to stay in more, open doors and windows less, turn up the central heating etc. Consequently there is less natural air change. 

In a nut shell, the higher the air temperature, the more water vapour the air is able to contain per cubic metre. At a certain temperature, the air is unable to contain any more mass of water vapour. When the temperature drops, that volume of air cannot hold any more vapour and it condenses out on colder surfaces such as windows and cold external walls. Condensation being a surface phenomenon combined with warm temperatures provides a breeding ground for black mould. 

Typical scenarios where we find black mould are:

Wardrobes sited on external walls, top and bottom corners of walls in rooms where the other side is exposed to the weather i.e. not internal dividing walls, ceilings in bathrooms and bedrooms which are not insulated or poorly insulated, behind furniture situated against external walls etc etc.  there are of course many other cases. 

To get top the point, high humidity levels, cold surfaces, poor air circulation and bad lifestyle habits cause condensation and black mould which can have ill health consequences for the occupants. 

Black mould is often mis-diagnosed as being related to rising or penetrating damp which can contribute but which is not often the primary root cause.  

There are things one can do to improve the building fabric of your home and to develop good habits relating to lifestyle within the home as follows:

Insulate cold surfaces, improved correctly installed AND commissioned automatic humidity tracking ventilation, block up passive vents which can make matters worse for various reasons, better management of central heating. Aim for a constant base temperature rather than full on during the day and switched off at night which encourages dumping of excess moisture in the air on cold surfaces. 

A properly qualified experienced specialist surveyor will be able to give advice. Look for PCA (Property Care Association) qualification and accreditation. The PCA are THE national governing body for matters such as this which relate to dampness, water ingress and secondary issues such as mould, decay, woodworm infestation and the like. 

The question of whether you should pay for a survey crops up very frequently. the matter of payment in itself is not relevant in my opinion. Payment relates to what you are getting for the money. You should be paying for expertise, experience, professionalism, is a report included, is there a guarantee?

Usually you get what you pay for. Those offering free surveys MAY use that as an incentive to get a foot in the door and you will pay for the survey in the works which are recommended and ultimately carried out. You may wish to consider the above but don’t write off paying for the survey if there are obvious benefits. One could argue that paying for a damp survey is more transparent and ethical if you feel there are benefits and peace of mind. Ask the surveyor about the above before you commit would be my advice.